Re: NaN-toolbox much faster now

[Alois Schlögl]

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John W. Eaton wrote:
> On 17-Mar-2009, Alois Schlögl wrote:
> 
> | I guess this comes from the old days (around Octave 2.0 and 2.1) when
> | there were really much to many global flags used much too often.
> | 
> | However, a general ban on on the use of global flags is going to far, IMHO.
> | 
> | OTOH, if global variables within functions are really "harmful", it
> | would be only consequent to enforce this rule by preventing the
> | use of global variables within functions. ;-)
> 
> Global variables are not always bad.
> 
> Even some global option variables are OK.  For example, those that
> simply change an output format or the appearance of a prompt don't
> cause much trouble because almost no code depends on those settings,
> and they are highly unlikely to cause a computation to produce
> incorrect results.
> 
> But settings that affect the way code is parsed, or that cause a
> function to produce different results for the same input are harmful.
> I don't want to see any more of those introduced in Octave.
> 
> I also don't want Octave to differ from Matlab when computing mean,
> std, etc., because I think doing so will generate bug reports.
> 
> jwe


Dear John,

Both implementations are doing the same thing, they estimate the mean,
variance, standard deviation, etc. The only difference is that one
implementation gives more often NaN (indicating no result) than the
other implementation. Maybe its not wrong to return NaN, but its not
what you want. You want the best possible estimate.

Therefore, I expect no or very little bug reports. If there are any,
these can be easily handled (pointing them to the discussion, the readme
or a wiki). And in worst case, IF (not when) someone is getting into a
serious compatibility problem, a parachute is in place with
flag_implicit_skip_nan(0); again, I do not expect any need for it.

Cheers,
  Alois



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